The present invention relates to an electrohydraulic drawing apparatus, particularly a hoist, for pulling or lifting and lowering loads, comprising a cylinder piston unit, a hydraulic fluid tank, a pump coupled to an electric motor and connected to the cylinder piston unit, control means for the electrical and hydraulic control of the drawing apparatus, and a load lifting member.
Small hoist of this species are already known in the art. With simple, economical electromechanical designs, the lift and lowering speed is nearly constant or selectable in two stages by pole reversal of the motor. Pneumatic hoists or balancers permit a continuously variable speed regulation, but produce a greatly annoying noise or have the disadvantage that the load tends to vibrate due to the compressibility of the air. Hydraulic devices permit a continuously variable adaptation of the speed, as well as a sensitive and accurate positioning of the load, but their known designs are relatively complex and therefore expensive.
It is, therefore, an object of the present invention to provide a simple and economical hoist where the load sensitively follows the vertical motions of a controlling hand.
Another object of the present invention is to provide apparatus of the foregoing character which may be readily maintained in service and has a substantially long operating life.